While removable liners present many advantages, one major disadvantage associated with removable liners is that the foot of an athlete wearing a snowboard boot with a removable liner has a tendency to slip and move within the boot. This slipping may be caused by the athlete's foot moving within the liner, by the liner moving within the boot, or by a combination of these two phenomena. The most common result of this slipping is that the heel of the athlete lifts up from the bed of the boot. This slipping and lifting makes it more difficult for the athlete to control the snowboard, results in blisters and increases the likelihood of more serious injuries to the athlete.
This slipping problem has been found in the context of ski boots. Multiple solutions to this problem in the field of ski boots have been presented including several variations on the theme of using an air bladder positioned at various locations between the foot of the athlete and the exterior of the boot. Air bladders also have been used in other types of footwear for various purposes.
This invention is specifically concerned with snowboard boot liners made of EVA having an inflatable air bladder incorporated therein and the mass production of such liners.
Holstine, U.S. Pat. No. 5,692,321 discloses an athletic boot such as a snowboard boot having a bladder system consisting of an upper and lower bladder in communication with each other disposed between the wearer's foot and the exterior of the boot. The upper and lower bladder system is a closed system. Thus, the overall inflation level of the bladder system is fixed and may not be readily adjusted. The system disclosed in Holstine is designed to give increased support to the ankle of a wearer when downward forces compress the lower bladder causing a corresponding inflation of the upper bladder. Holstine stresses that the disclosed boot provides the athlete with increased flexibility and range of motion of the athlete's foot when impact or operational forces are removed from the boot. Holstine does not disclose how his boot is to be produced.
Potter, et al., U.S. Pat. No. 5,765,298 discloses an athletic shoe with an inflatable bladder present in the ankle collar. The bladder has weld fines or other means incorporated therein to prevent the formation of restrictive vertical columns of pressurized gas in the medial and lateral section of the bladder. This allows increased flexibility and mobility of the wearer's ankle. Potter, et al. do not disclose how their product is to be produced.
Nishimura U.S. Pat. Nos. 3,744,159 and 3,758,964 disclose sports shoes containing an inflatable air bladder. The majority of Nishimura's disclosures focus on ski boots containing inflatable air bladders. Nishimura does not disclose the methods used to manufacture his products. Nor does Nishimura disclose the use of EVA as a liner material.
None of the foregoing prior art have suggested snowboard boot liners made of EVA having an inflatable air bladder incorporated therein and the mass production of such liners.